Perhaps I dont explain properly. Or perhaps I don't understand what you mean - or perhaps we think the same thing.I think I disagree or perhaps misunderstand. When a raw file is opened in acr and then opened in photoshop it is a tiff or a psd (unless opened as an object) with the acr changes baked in. That tiff or psd is no longer a raw file but is now rasterized/pixel based. The conversion is lossless for sure. Using the canera raw filter is now fighting against the baked in changes
Your raw file will always be just that - as shot.
Any changes you do in LR or ACR is separate and can be deleted.
If you do an edit in ACR for instance - eg crop - and then open the file directly from ACR in Photoshop (not as an object) you still have a Raw file (or a file that is nothing yet?) , until you save it out as something else (jpeg/psd)
but my point is - once you crop in ACR - and then take the file into PS - and continuing editing - you are now 6 layers later - and decide the crop is not what you wanted. You are stuck - you have to go back to your original Raw file. Open it again in ACR and un-do the crop before you can again apply the rest of your edits. Thats what I mean you have fixed a change in place (the crop) and you can not undo it unless you go back to scratch.
That's how I have it. If you opened it as an Object - then you can go back into ACR. How it would affect the rest of your images adjustments, would depend on what steps you did after opening the object in PS.
I am open to correction of course.